Hypoxia modulates the undifferentiated phenotype of human renal inner medullary CD133+ progenitors through Oct4/miR-145 balance.
ABSTRACT Low-oxygen tension is an important component of the stem cell microenvironment. In rodents, renal resident stem cells have been described in the papilla, a relatively hypoxic region of the kidney. In the present study, we found that CD133(+) cells, previously described as renal progenitors in the human cortex, were enriched in the renal inner medulla and localized within the Henle's loop and thin limb segments. Once isolated, the CD133(+) cell population expressed renal embryonic and stem-related transcription factors and was able to differentiate into mature renal epithelial cells. When injected subcutaneously in immunodeficient mice within Matrigel, CD133(+) cells generated canalized structures positive for renal specific markers of different nephron segments. Oct4A levels and differentiation potential of papillary CD133(+) cells were higher than those of CD133(+) cells from cortical tubuli. Hypoxia was able to promote the undifferentiated phenotype of CD133(+) progenitors from papilla. Hypoxia stimulated clonogenicity, proliferation, vascular endothelial growth factor synthesis, and expression of CD133 that were in turn reduced by epithelial differentiation with parallel HIF-1α downregulation. In addition, hypoxia downregulated microRNA-145 and promoted the synthesis of Oct4A. Epithelial differentiation increased microRNA-145 and reduced Oct4 level, suggesting a balance between Oct4 and microRNA-145. MicroRNA-145 overexpression in CD133(+) cells induced downrelation of Oct4A at the protein level, inhibited cell proliferation, and stimulated terminal differentiation. This study underlines the role of the hypoxic microenvironment in controlling the proliferation and maintaining a progenitor phenotype and stem/progenitor properties of CD133(+) cells of the nephron. This mechanism may be at the basis of the maintenance of a CD133(+) population in the papillary region and may be involved in renal regeneration after injury.
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ABSTRACT: The existence and identification of adult renal stem cells is a controversial issue. In this study, renal stem cells were identified from cultures of clonal human nephrospheres. The cultured nephrospheres exhibited the activation of stem cell pathways and contained cells at different levels of maturation. In each nephrosphere the presence of 1.12-1.25 cells mirroring stem cell properties was calculated. The nephrosphere cells were able to generate three-dimensional tubular structures in 3D cultures and in vivo. In clonal human nephrospheres a PKH(high) phenotype was isolated using PKH26 epifluorescence, which can identify quiescent cells within the nephrospheres. The PKH(high) cells, capable of self-renewal and of generating a differentiated epithelial, endothelial and podocytic progeny, can also survive in vivo maintaining the undifferentiated status. The PKH(high) status, together with a CD133(+)/CD24(-) phenotype, identified a homogeneous cell population displaying in vitro self-renewal and multipotency capacity. The resident adult renal stem cell population isolated from nephrospheres can be used for the study of mechanisms that regulate self-renewal and differentiation in adult renal tissue as well as in renal pathological conditions.Stem cell research 08/2013; 11(3):1163-1177. · 3.39 Impact Factor
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ABSTRACT: Living organisms are constantly exposed to environmental and genetic perturbations. Biological robustness enables these organisms to maintain their functional stability in the presence of external or internal changes. It has been proposed that microRNAs (miRNAs), small non-coding regulatory RNAs, contribute to robustness of gene regulatory networks. The hypoxic response is a major and well-characterized example of a cellular and systemic response to environmental stress that needs to be robust. miRNAs regulate the response to hypoxia, both at the level of the main transcription factor that mediates this response, the hypoxia-inducible factor (HIF), and at the level of one of the most important systemic outcomes of the response: angiogenesis. In this review, we will take the hypoxic response as a paradigm of miRNAs participating in circuits that provide robustness to biological responses. Developmental Dynamics, 2012. © 2012 Wiley Periodicals, Inc.Developmental Dynamics 09/2012; · 2.59 Impact Factor
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ABSTRACT: Different approaches for the isolation of stem/progenitor cells have been reported, including stem cell selection in stringent culture conditions. We evaluated the possibility of isolating human progenitor cells from surgical specimens preserved by under vacuum sealing and cooling, a clinical practice approached by several hospitals as alternative to formalin. Renal tissue samples (n = 20) maintained under vacuum from 6 to 48 h at 4°C were used to isolate human renal CD133 (+) progenitor cells. We obtained CD133 (+) progenitors from unsorted cells derived from disaggregated tissues from each sample. Phenotypic characterization as well as in vitro and in vivo differentiation of the obtained CD133 (+) lines showed results comparable with sorted CD133 (+) cells obtained from fresh tissue. These results indicate that the process of sealing under vacuum and cooling appears as a suitable tissue treatment to isolate hypoxia resistant cells, such as human stem/progenitor cells, and that this procedure can be exploited to render the extraction of stem cells from human samples more practical and feasible.Organogenesis 07/2012; 8(3). · 2.28 Impact Factor